Ronde & Schwarz 1304.0004K03, Руководство пользователя

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The Spectrum Application (RF Measurements)
R&S
®
FPL1000
323 User Manual 1178.3370.02 ─ 11
Number of subspans
Several analysis steps are required to cover the entire span, in particular if the span
exceeds the maximum I/Q bandwidth for a single measurement. In this case, each FFT
analysis covers a subspan. The subspan cannot be defined directly, but it can be opti-
mized according to measurement requirements, as described above. The number of
required subspans is indicated in the sweep settings dialog box. Thus, you can deter-
mine the required measurement time for an individual span (and thus sweep point) as:
<Meas time subspan> = <sweep time> / <no. of subspans>
6.6.1.6 Which Data May Pass: Filter Types
While the filter is irrelevant when measuring individual narrowband signals (as long as
the signal remains within the RBW), the measurement result for broadband signals is
very dependant on the selected filter type and its shape. If the filter is too narrow, the
signal is distorted by the filter. If the filter is too wide, multiple signals can no longer be
distinguished. Generally, the smaller the filter width and the steeper its edges, the lon-
ger the settling time and thus the longer the "Sweep Time" must be.
All resolution bandwidths are realized with digital filters. Normal (3dB) Gaussian filters
are set by default. Some communication standards require different filters.
For a list of available filter types, see Chapter 6.6.3, "Reference: List of Available RRC
and Channel Filters" , on page 333.
Normal (3 dB) Gaussian filters
Gaussian filters provide a good compromise between steep edges and a short settling
time. This filter is suitable for most measurement tasks and is used by default.
The available Gaussian (3 dB) filters are listed in the R&S FPL1000 data sheet.
Channel filters
Channel filters are fairly steep but require a long settling time; they are useful for pulse
measurements in the time domain.
6.6.1.7 How Long the Data is Measured: Sweep Time
Each filter has a settling time that must be awaited in order to obtain correct results.
Since the resolution bandwidth and video bandwidth define the filter, the smaller of the
two determines the minimum "Sweep Time" required for the measurement. Allowed
values depend on the ratio of span to RBW and RBW to VBW.
If the selected "Sweep Time" is too short for the selected bandwidth and span, level
measurement errors will occur. In this case, the R&S
FPL1000 displays the error mes-
sage "Sweep time too low" and marks the indicated "Sweep Time" with a red bullet.
Furthermore, a status bit indicates an error.
(For more information see Chapter 9.2.2.14, "STATus:QUEStionable:TIMe Register" ,
on page 563.)
Bandwidth, Filter and Sweep Configuration